Orthopedic casts are typically made by stationarily positioning the body part to be immobilized and circumferentially wrapping a length of pliant, hardenable tape in both lateral and circumferential overlapping relationship around the body part until sufficient wraps have been made to provide a cast which extends the length of the body part to be immobilized and has sufficient cross-sectional dimension to provide the necessary strength, rigidity, and durability to meet the demands recognized as necessary for orthopedic casts.
Many synthetic orthopedic casting tapes currently used comprise a fabric bandage, usually fiberglass, which is impregnated with a liquid resin which hardens upon exposure to moisture. Such casting bandages are described, for example, in U.S. Pat. Nos. 4,502,479, 4,433,680 and 4,376,438. Such casting bandages are typically provided in rolls of tape two to five inches (5.08 to 12.7 cm) wide, which are wrapped around the injured body member prior to hardening. Generally, multiple layers of the bandage are required to achieve the desired strength and rigidity. Since the bandage is often wrapped around body contours such as heels, elbows, etc., it is often necessary to make tucks or folds in the bandage, and a high level of skill is required in cast application in order to achieve a uniform, well-fitting cast. This problem has been somewhat alleviated by the introduction of highly extensible knit fabrics such as those used in "Scotchcast 2" casting materials available from 3M and described in copending application Ser. No. 668,881, filed Nov. 6, 1984 and assigned to the same assignee as the present invention. Such extensible fabric bandages can be more easily applied and will conform to body contours without the need for tucking and folding. However, the application must still be accomplished by a winding and wrapping process involving a plurality of overlapping layers.
In addition to tape bandages, a number of orthopedic casting systems more adapted to particular body parts have been devised. For example, U.S. Pat. Nos. 2,759,475 and 2,800,129 show blanks for forming splints comprising a solid thermoplastic material provided on one surface with a foam plastic layer. The blank is heated to a temperature such that the solid thermoplastic material becomes soft, and is then applied to the body part and shaped to form the splint. Similarly, U.S. Pat. No. 4,442,833 shows a casting or splinting bandage comprising a closed-cell polymer foam and a plurality of sheets of a textile material impregnated with a water curable resin. All three of these systems are described as further utilizing tapes, bandages or the like to aid the more shaped portion of the system in supporting the body part.
Apart from systems utilizing some form of tape, there are a number of casting systems utilizing reactive foams which are in situ hardened to form a closed cell foam around the body part. It is believed that those systems are generally difficult to handle, require a propellent, or come in a two part system requiring mixing. Hence, these systems are believed to be inconvenient to use, require a relatively high level of skill to apply and result in an occlusive cast construction that may promote patient skin masceration.